Looping to give loaded progress

1

I am trying to create a loop that will display the loaded progress of an image.

I have the following code but cant get it to loop to show the progress:

l = this._parent.photo.getBytesLoaded();
	t = this._parent.photo.getBytesTotal();
	if(l < t)
	{
		textbox.text = "Loading (" + l + " bytes of: " + t +")";
	}
	if(l == t)
	{
		textbox.text = "done";
	}

Please help!